Method and system for sharing convergence data

ABSTRACT

Systems and methods for sharing convergence data between GNSS receivers are disclosed. Convergence data received at a GNSS receiver via a communication connection may be utilized to determine a position of the GNSS receiver.

BACKGROUND

The Global Positioning System (GPS) and its counterparts in the GlobalNavigation Satellite System (GNSS) have become thoroughly pervasive inall parts of human society. GPS and GNSS receivers are increasinglybeing integrated into devices, tools, and vehicles such as agriculturalvehicles, construction equipment, and even in autonomously operatedvehicles. In order to provide position measurements with a necessarydegree of precision, GNSS receivers may be configured to utilizecorrections from various sources. Examples of these correction systemsinclude, for example, the Wide Area Augmentation System (WAAS), theSatellite-Based Augmentation System (SBAS), the Real-time Kinematic(RTK) technique, the Precise Point Positioning (PPP) technique, theEuropean Geostationary Navigation Overlay Service (EGNOS), and the like.Using correction data from these sources, a GNSS receiver can accountfor error sources such as atmospheric delay of GNSS signals, clockerrors, and ephemeris errors to derive a more precise position fix.

When a GNSS receiver (or rover) uses correction data from a singlereference station (e.g., differential GPS (DGPS) or RTK), there aresmall bias errors in the corrections for each satellite that are subjectto both temporal and spatial decorrelation. With temporal decorrelation,the correction data degrades as time increases since the referencemeasurements were taken. With spatial decorrelation, the correction datadegrades as distance increases between the rover and the site where thereference measurements were taken.

These correction bias errors also exist in systems that use networkedreference stations such as SBAS or PPP. Because there is no referencestation at the exact rover site, there will be small correction biaserrors. These errors are influenced most heavily by atmosphericconditions—ionospheric model error and tropospheric model error. Thesecorrection bias errors will be similar for all rovers within a fewkilometers of each other, and will change slowly over time, on the orderof minutes, as atmospheric conditions change.

By observing the corrections over a large number of measurements, therover can estimate the correction bias errors. This process, calledconvergence, can substantially reduce the magnitude of measurementerror. A detailed discussion of typical convergence techniques is foundin “IMPROVED CONVERGENCE FOR GNSS PRECISE POINT POSITIONING”, by S.Banville, Ph.D. dissertation, Department of Geodesy and GeomaticsEngineering, Technical Report No. 294, University of New Brunswick,Fredericton, New Brunswick, Canada, which is incorporated herein byreference. If enough measurements are taken, and the network model is ofsufficiently high fidelity, it may be possible for the bias errorestimates to converge to centimeter level accuracy, in which case it maybe possible to resolve carrier phase ambiguities to provide a positionfix with centimeter level accuracy. This occurs more quickly on amulti-frequency band rover where the ionospheric model error is not asonerous as on a single frequency band rover. However, even without fullinteger ambiguity resolution, a single frequency band rover will benefitfrom reduced correction bias errors, and can often attain positioning tosub-meter accuracy after sufficient convergence. Thus, systems andmethods for reducing convergence times are desired.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate embodiments that, together with thedetailed description, serve to explain various features and principlesof some embodiments. Unless noted, the drawings referred to in thisbrief description should be understood as not being drawn to scale.Herein, like items are labeled with like item numbers.

FIG. 1 is a simplified diagram showing a GNSS receiver sendingconvergence data to another GNSS receiver in accordance with variousembodiments.

FIG. 2 is a flowchart of a method for sharing convergence data betweenGNSS receivers in accordance with various embodiments.

FIGS. 3A-3C are block diagrams of components of a convergence datasharing system in accordance with various embodiments.

FIG. 4A-4F show the use of systems for sharing convergence data inaccordance with various embodiments.

FIG. 5 is a diagram of an exemplary GNSS receiver that may be used inaccordance with various embodiments.

FIG. 6 is a diagram of an exemplary convergence data server that may beused in accordance with various embodiments.

FIG. 7 is a flowchart of a method for sharing convergence data inaccordance with various embodiments.

DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. While variousexamples are discussed herein, it will be understood that they are notintended to limit the embodiments. On the contrary, the scope of thisapplication is intended to cover alternatives, modifications, andequivalents, which may be included within the spirit and scope of thevarious embodiments as described herein and defined by the appendedclaims. Furthermore, numerous specific details are set forth in order toprovide a thorough understanding of embodiments of the present subjectmatter. However, embodiments may be practiced without these specificdetails. In other instances, well known methods, procedures, components,and circuits have not been described in detail so as to notunnecessarily obscure aspects of the described embodiments.

Rovers can estimate correction bias errors by observing a large numberof measurements. These bias estimates are refinements to correction datareceived from external sources such as base stations or network controlcenters. The convergence process can improve bias estimates allowingincreased accuracy in position measurements performed by the rover. Theconvergence process is time consuming, however, and can take up to ahalf hour before sufficiently refined convergence data is obtained.Multi-frequency band rovers typically achieve convergence more quicklythan single-frequency band rovers, but the convergence process takestime for all rovers regardless of their capabilities.

Since correction bias errors are common to all rovers in the sameapproximate area, one rover that is un-converged (or operating in anon-converged state) can use the bias estimates (or convergence data)that have been generated by another nearby rover that has alreadyconverged. The form of the convergence data passed from one rover toanother may vary according to the particular rover models, so it isexpected that both rovers use similar systems in some embodiments.Typical convergence data might include adjustments (or refinements) tothe atmospheric models. The convergence data may also include orbitmodels and/or satellite clock errors. By using bias estimates fromanother rover that has already converged, the convergence time can bereduced.

FIG. 1 is a simplified diagram showing a GNSS receiver sendingconvergence data to another GNSS receiver in accordance with variousembodiments. In this example, a first GNSS receiver 111 a that is in aconverged state sends its convergence data to a second GNSS receiver 111b that is in an un-converged state. The convergence data may be used bythe second GNSS receiver 111 b to determine position measurements.Receiving and using the convergence data from the first GNSS receiver111 a allows the second GNSS receiver 111 b to accurately determine itsposition much more quickly than if it were to generate its ownconvergence data using conventional processes.

The convergence data may be shared between the GNSS receivers usingwired or wireless communication connections. In some embodiments, forexample, the convergence data is shared using wireless radio, cellular,and/or satellite communication connections. The GNSS receivers may beeither mobile or stationary. Mobile GNSS receivers may be those that arearranged in a handheld device (e.g., handheld GPS or cellulartelephone), arranged in a larger movable device (e.g., survey rover), orintegrated as part of a larger mobile structure (e.g., vehicle ortractor). The GNSS receivers shown in FIG. 1 may be different (e.g., thefirst GNSS receiver 111 a may be arranged in a cellular telephone whilethe second GNSS receiver 111 b may be arranged in a survey rover), butthey will typically use similar differential positioning techniques(e.g., PPP techniques).

The convergence data provided by the first GNSS receiver 111 a to thesecond GNSS receiver 111 b may include refinements to correction data.The correction data is received from external sources. The correctiondata is data that is used in PPP (PPP correction data) or otherdifferential positioning techniques. The correction data may includeatmospheric models (e.g., ionospheric and/or tropospheric modelingerrors), orbit models (e.g., ephemeris data), and/or satellite clockerrors. The correction data may be produced at a central location whereprecise orbits and clocks of all tracked navigation satellites aregenerated and updated in real time. Atmospheric conditions that delaythe propagation of the signals from the satellites may also bedetermined. The correction data is broadcast or otherwise provided toGNSS receivers, typically by satellite service or cellular link, but canbe done by any of a number of communications links.

One or more processors in the GNSS receiver utilize the correction dataalong with other signal measurements to produce convergence data thatallows centimeter level positioning. As an example, PPP correction datamay be used to generate PPP convergence data. In addition to refinedcorrection data, the convergence data may also include code phase and/orcarrier phase measurements, resolved carrier phase ambiguities, anuncertainty estimate of each code phase and/or carrier phase bias,correlations associated with each received GNSS signal, and time-tagsfor each received GNSS signal. The convergence data may also include oneor more position fixes of the first GNSS receiver 111 a and/or how longcontinuous tracking of GNSS signals from particular satellites has beenmaintained. The second GNSS receiver 111 b can use the convergence datato achieve centimeter level precision almost immediately rather thangenerating its own convergence data using conventional processes.

FIG. 2 is a flowchart of a method for sharing convergence data betweenGNSS receivers in accordance with various embodiments. The methodincludes receiving convergence data at a first GNSS receiver from asecond GNSS receiver (1001). The first GNSS receiver is operating in anon-converged state and the second GNSS receiver is operating in aconverged state. The convergence data is generated at the second GNSSreceiver using correction data from one or more base stations. The firstGNSS receiver and/or the second GNSS receiver may be mobile GNSSreceivers, and the convergence data may be PPP convergence data. Themethod also includes determining a position of the first GNSS receiverusing the convergence data received from the second GNSS receiver(1002).

FIGS. 3A-3C and 4A-4F and the accompanying text provide examples ofspecific applications where convergence data can be used by GNSSreceivers to quickly obtain accurate position measurements. Theseexamples illustrate the usefulness of sharing convergence data. It isrecognized that the various embodiments described herein may be extendedto many other receiver-to-receiver applications, and while many of thefollowing examples describe vehicle-to-vehicle implementations, theseimplementations could be extended to any combination of vehicles, mobiledevices, drones, survey receivers, geographic information system (GIS)devices, equipment for mining or agriculture, manned or unmannedaircraft, cranes, and the like.

FIG. 3A shows some components used in a convergence data sharing system100 in accordance with various embodiments. In FIG. 3A, convergence datasharing system 100 comprises a convergence data server 101 that furthercomprises a data storage device 102 and a wireless communicationtransceiver 103. For the purpose of the present application, the term“convergence data server” refers to a device that receives, stores, andcommunicates convergence data. In accordance with various embodiments,convergence data server 101 may comprise a computer system that isconfigured to receive convergence data (e.g., using wirelesscommunication transceiver 103) from a converged GNSS receiver, to storethe convergence data (e.g., in data storage device 102), and to conveythe convergence data to another GNSS receiver that may or may not be ina converged state. In accordance with various embodiments, theconvergence data may be conveyed from convergence data server 101 to theGNSS receiver directly or via an intervening communication device.

The data storage device 102 may be any type of device configured fordata storage. The data storage device 102 may be integrated with anotherdevice, such as the convergence data server 101, or it may be a separatedevice. Also, the data storage device 102 may be configured fortemporary or permanent data storage. Other examples of data storagedevices are provided throughout the description.

In accordance with various embodiments, convergence data sharing system100 can receive the convergence data from, for example, a passing carhaving a converged GNSS receiver that conveys this data to convergencedata sharing system 100 via wireless communication transceiver 103. Whenanother vehicle having a non-converged GNSS receiver passes by,convergence data server 101 may detect the GNSS receiver and convey theconvergence data via wireless communication transceiver 103. The passingvehicle can then use the convergence data to quickly achieve accuratepositioning.

In accordance with various embodiments, convergence data server 101 mayselect from a plurality of convergence data based upon at least onecriteria as described more fully below. In accordance with at least oneembodiment, the criteria may also be conveyed from convergence dataserver 101 to the GNSS receiver which may use that data to perform itsown selection process.

The United States Department of Transportation (U.S.D.O.T.) has beenconducting research in cooperation with automotive manufacturers todeveloping a system that utilizes vehicle-to-vehicle communications towirelessly exchange vehicle-based data such as location, position, andspeed (also referred to as V2V systems). Using this information, avehicle will be able to maintain awareness of other nearby vehicles,calculate potential risks, issue warnings, or take pre-emptive actionsto avoid dangerous situations. In general, the vehicular networkscomprise two types of nodes: vehicles and roadside stations. Both typesof nodes utilize a dedicated short-range communications (DSRC) network.The specification for the DSRC network prescribes operation in the 5.9GHz band with a bandwidth of 75 MHz and an approximate range of 1000meters. Two categories of standards provide outlines for vehicularnetworks. These standards constitute a category of IEEE standards for aspecial mode of operation designed for vehicular networks. IEEE 802.11pis an extension to the 802.11 Wireless LAN medium access layer (MAC) andphysical layer (PHY) specification. IEEE 802.11p aims to providespecifications needed for MAC and PHY layers for specific needs ofvehicular networks. The IEEE 1609 is a family of standards that isdirected to management and security of the DSRC network. In accordancewith various embodiments, wireless communication transceiver 103 iscompliant with the IEEE 802.11p specification for implementing a DSRCnetwork. However, it is noted that in accordance with variousembodiments, other types of wireless communication transceivers can beimplemented as described in greater detail below.

Some of the examples provided herein are described with reference to V2Vsystems. It should be appreciated that these examples may be extended toany vehicle-to-infrastructure (V2I) or vehicle to anything (V2X)implementations.

FIG. 3B shows components used in a convergence data sharing system 110for sharing convergence data in accordance with various embodiments. Forthe purpose of brevity, the components described above with reference toFIG. 3A will not be described again in detail. In FIG. 3B, convergencedata sharing system 110 comprises a convergence data server 101. Theconvergence data server 101 further comprises a data storage device 102and a wireless communication transceiver 103 as described above. In FIG.3B, convergence data sharing system 110 further comprises a GNSSreceiver 111 coupled with convergence data server 101.

In accordance with various embodiments, once GNSS receiver 111 hasachieved convergence, it will determine new convergence data on anepoch-by-epoch basis (e.g., each second, each half second, etc.) andstore the convergence data in data storage device 102. In accordancewith various embodiments, GNSS receiver 111 comprises a multi-frequencyband GNSS receiver. For example, GNSS receiver 111 may be configured toreceive and process GPS signals in the L1, L2C, and/or L5 frequencybands. This is advantageous since receiving GNSS signals in multiplefrequency bands tends to shorten the time for GNSS receiver 111 toautonomously achieve convergence. The use of two or more GNSS frequencybands from the same satellite facilitates determining ionosphericeffects, since the ionospheric effects are in part dependent upon theradio frequency. The GNSS signals on various frequency bands may bephase locked (e.g., in phase with each other) since the same clocksignal is used at the broadcasting satellite to modulate the signals.The timing difference between the reception of two or more GNSS signalsis largely a function of the atmospheric conditions and broadcastfrequency bands of the two or more signals. Thus, various embodimentsuse differences in the time the signals were received to determine theelectron density of the ionosphere. In so doing, the ionospheric delayof GNSS signals can be removed from the determination of thesatellite-receiver distance to improve positioning accuracy.

Furthermore, by using two GNSS frequency bands from the same satellite,a process known as “wide-laning” can be performed. Using GPS as anexample, the L2C or L5 signal band (e.g., 1227.60 MHz or 1176.45 MHzfrequency bands respectively) may be subtracted from the L1 signal band(e.g., 1575.41 MHz frequency band). This results in a third signal witha frequency band of 347.81 MHz when the L2C signal band is used or afrequency band of 398.45 MHz when the L5 signal band is used. This lowerfrequency band signal has a correspondingly longer wavelength. As aresult, it is easier to narrow the field of candidate carrier integerswhich are then processed to determine the corresponding carrier integer.In accordance with various embodiments, wide-laning may be used toexpedite re-acquisition of the L1 carrier phase signal. In anotherembodiment, a process known as “tri-laning” can be performed in whichthe L2C signal band is subtracted from the L1 signal band and the L5signal band is subtracted from the L1 signal band. The resulting lowerfrequency signals overlap to some extent and this allows narrowing thefield of candidate integers which are then processed to determine thecorresponding carrier integer.

Thus, in some embodiments, once convergence has been achieved, thebiases received for the L1 signal band from a given satellite are usableby an L1-only user who receives the L1 biases from convergence dataserver 101. In other words, while receiver 111 may resolve the biases inthe L1, L2/L2C, and/or L5 frequency band range, it may pass the biasesof only one (e.g., L1, L2C, or L5) frequency band range to a passingvehicle in some embodiments. Other GNSS systems besides GPS may shareconvergence data in a similar manner.

In accordance with various embodiments, convergence data sharing system110 can autonomously derive the convergence data described above that isthen shared (e.g., conveyed using wireless communication transceiver103) to a non-converged GNSS receiver such as in a car, truck, othervehicle, or any other receiver-to-receiver implementation. In accordancewith various embodiments, convergence data sharing system 110 can querya passing vehicle as to whether it needs convergence data.Alternatively, a convergence data sharing system 110 located in avehicle which is not currently converged can generate a query todetermine whether there are any proximate convergence data servers(e.g., 101 of FIGS. 3A, 3B, and/or 3C) that have current convergencedata available for sharing. In accordance with some embodiments, currentconvergence data is data that has been generated less than somethreshold (e.g., 5 minutes) from the current time.

In accordance with various embodiments, convergence data sharing system110 can be installed at various locations where traffic is likely topass, such as highway on-ramps, entrances/exits of tunnels, bridges,parking structures, fire stations, etc. When a passing vehicle isdetected using the V2V communication protocol, for example, convergencedata sharing system 110 can provide the convergence data to the GNSSreceiver of that vehicle to facilitate convergence of the receiver. Inso doing, the vehicle will be able to achieve convergence of its ownGNSS receiver almost instantly upon reception of the convergence data.

Additionally, in accordance with various embodiments, convergence datasharing system 110 can be located in another vehicle. In other words, aconverged GNSS receiver 111 located in a vehicle can pass theconvergence data to another nearby vehicle. The other vehicle can thenuse the convergence data to facilitate convergence of its receiver.

FIG. 3C shows components used in a convergence data sharing system 120for sharing convergence data in accordance with various embodiments. Forthe purpose of brevity, the components described above with reference toconvergence data sharing systems 100 and 110 of FIGS. 3A and 3Brespectively will not be described again in detail. In FIG. 3C, system120 comprises a plurality of convergence data servers (e.g., 101-1,101-2, and 101-N) that are respectively in communication with a cloudcomputing network 121 via a data connection enabled by their respectivewireless communication transceivers (e.g., 103-1, 103-2, . . . 103-N).

In accordance with various embodiments, the data connection betweenconvergence data servers 101-1, 101-2, and 101-N and cloud computingnetwork 121 can be a wired data connection, a wireless data connection,or a combination of both. It is noted that there is no limit on how manyconvergence data servers 101 can be coupled with cloud computing network121 in accordance with various embodiments.

In FIG. 3C, cloud computing network 121 is used as the data storagedevice of convergence data servers 101-1, 101-2, and 101-N in place ofor in conjunction with a local data storage device. In accordance withvarious embodiments, cloud computing network 121 is configured tocollect, store, and disseminate convergence data that is indexed by timeand location. For example, cloud computing network 121 may be coupledwith one or more of convergence data servers 101-1, 101-2, and 101-N andconfigured to receive and store convergence data that has been conveyedto them. Later, a vehicle passing one of the convergence data servers101-1, 101-2, and 101-N can convey a request for current convergencedata for the location at which it is located. Convergence data servers101-1, 101-2, and 101-N may then pass the request for convergence data,along with the current time and location, to cloud computing network121. Cloud computing network 121 may determine whether there is anyusable convergence data available (e.g., current within a predeterminedtime period and within a predetermined radius of the querying vehicle).If cloud computing network 121 determines that there is usableconvergence data available, it will forward it to the appropriate dataservers 101-1, 101-2, 101-N, which will forward it to the vehicle usinga wireless communication transceiver 103.

FIG. 4A shows the use of a system for sharing convergence data inaccordance with various embodiments. In FIG. 4A, a first vehicle 201comprising a first convergence data sharing system (e.g., convergencedata server 101-1 and GNSS receiver 111-1) is passing a second vehicle202 also comprising a second convergence data sharing system (e.g.,convergence data server 101-2 and GNSS receiver 111-2). For the purposesof illustration, it is assumed that GNSS receiver 111-1 is a convergedGNSS receiver and GNSS receiver 111-2 is a non-converged GNSS receiver.Typically, a V2V system will operate in a mode in which it is searchingfor and discovering other V2V systems in its vicinity. As the V2Vstandard allows for a range of approximately 1000 meters, it is onlycapable of discovering other V2V devices within a limited area. Inaccordance with various embodiments, when the GNSS receiver of a vehicleis not in a converged state, the wireless communication transceiver mayconvey a message indicating that convergence data is needed to other V2Vsystems in its vicinity. In FIG. 4A, once convergence data servers 101-1and 101-2 have established communications (e.g., communicationconnection 250), convergence data server 101-2 will send a messageindicating that GNSS receiver 111-2 is not operating in a convergedstate or is seeking convergence data. In accordance with variousembodiments, once convergence data server 101-1 receives the message, itwill access its own data storage device and retrieve the most recentconvergence data. Convergence data server 101-1 will then send theconvergence data to convergence data server 101-2 of second vehicle 202.

In a similar manner, if GNSS receiver 111-2 is operating in convergedstate, convergence data server 101-2 may “advertise” this status orinformation to other V2V systems in its vicinity.

FIG. 4B shows the use of a system for sharing convergence data inaccordance with various embodiments. In FIG. 4B, vehicle 203 is equippedwith a V2V system comprising convergence data server 101-3 and GNSSreceiver 111-3 (e.g., an implementation of convergence data sharingsystem 110 as described above with reference to FIG. 3B). For thepurpose of the following discussion, it is assumed that GNSS receiver111-3 is operating in a converged state. In this example, vehicle 203passes in the vicinity of convergence data sharing system 100,comprising a convergence data server as described above, andautomatically discovers convergence data sharing system 100 using theV2V protocols. It is noted that convergence data sharing system 100 doesnot comprise a GNSS receiver and instead receives, stores, anddisseminates convergence data from other converged GNSS receivers asthey pass nearby. In accordance with various embodiments, whenconvergence data sharing system 110 of vehicle 203 has established acommunication connection (e.g., 251A of FIG. 4B), it will convey that itdoes have convergence data. In accordance with various embodiments, whenthe convergence data sharing system of vehicle 203 receives a messagefrom convergence data sharing system 100 indicating that it does nothave convergence data, it will automatically access its data storagedevice and retrieve the latest convergence data. The convergence datasharing system of vehicle 203 will then automatically convey theconvergence data to convergence data sharing system 100. It is againnoted that this convergence data is time-tagged so that once theconvergence data is no longer valid (e.g., 5 minutes after it has beengenerated), it will not be used to attempt to attain convergence of anon-converged GNSS receiver. Convergence data sharing system 100 willstore this time-tagged convergence data in a data storage device.

At a later time (e.g., possibly when vehicle 203 is no longer present),a second vehicle 204 equipped with a convergence data sharing systemcomprising convergence data server 101-4 and GNSS receiver 111-4 passesconvergence data sharing system 100. For the purposes of the followingdiscussion, it is assumed that the GNSS receiver 111-4 of second vehicle204 is not operating in a converged state and convergence data sharingsystem 100 is storing usable convergence data. Again, second vehicle 204and convergence data sharing system 100 will automatically discover eachother using the V2V protocols and establish a communication connection252. Also, the convergence data sharing system of second vehicle 204will convey that it does not have convergence data. Because convergencedata sharing system 100 has received and stored convergence data fromvehicle 203 that is still valid based upon the time-tag, convergencedata sharing system 100 will automatically access its data storagedevice and convey the convergence data to the convergence data sharingsystem of second vehicle 204.

FIG. 4C shows the use of a system for sharing convergence data inaccordance with various embodiments. In FIG. 4C, a convergence datasharing system 110 comprising a convergence data server and a GNSSreceiver is located at an entrance ramp of a highway. A passing vehicle205 is also equipped with a convergence data sharing system comprisingconvergence data server 101-5 and GNSS receiver 111-5. In accordancewith various embodiments, the convergence data server of the roadsideconvergence data sharing system 110 and convergence data server 101-5 ofvehicle 205 automatically discover each other using the V2V protocolsand establish communications. Convergence data server 101-5 of vehicle205 conveys to convergence data sharing system 110 that it needsconvergence data. In accordance with various embodiments, theconvergence data server of the roadside convergence data sharing system110 will convey the convergence data to vehicle 205.

While the use of system 110 to share convergence data with non-convergedGNSS receivers has been described with reference to a roadsideconvergence data sharing system, the convergence data sharing system canbe located at any place where rapid convergence of a GNSS receiver isdesired. For example, vehicles leaving a mine shaft or traffic tunnelwill benefit from positioning of convergence data sharing system 110 atthe exit as the code phase and carrier phase biases of respective GNSSsignals can be lost when GNSS signals are blocked from a receiver. Otherexamples in which a convergence data sharing system 110 can be ofbenefit are locations where a vehicle may be shut off for an extendedperiod of time and thus lose track of the code phase and carrier phasebiases for respective GNSS signals. Some locations where this may provebeneficial include fire stations, police stations, parking structures,and vehicle storage yards (e.g., for construction equipment,agricultural vehicles, military vehicles, etc.). Thus, when a vehicle isstarted and begins to leave the location, it can receive convergencedata rather than having to wait and generate its own convergence datausing conventional processes.

FIG. 4D shows the use of a system for sharing convergence data inaccordance with various embodiments. In FIG. 4D, a vehicle 206comprising a convergence data sharing system passes a roadsideconvergence data sharing system 110. The vehicle's convergence datasharing system comprises a convergence data server 101-6 and GNSSreceiver 111-6, while the roadside convergence data sharing system 110comprises a convergence data server and GNSS receiver. In the example ofFIG. 4D, it is assumed that the convergence data sharing system ofvehicle 206 is operating in a converged state while the roadsideconvergence data sharing system 110 is operating in apartially-converged state. This may occur, for example, if there hasbeen a power outage that resulted in the roadside convergence datasharing system 110 losing track of GNSS signals. Upon restoration ofpower, the roadside convergence data sharing system 110 is thereforeoperating in a partially-converged state until it can autonomouslydetermine the biases of the received GNSS signals. It is noted thatwhile the roadside convergence data sharing system 110 may not havecompletely converged, it may still share those partially-convergedbiases with other systems in the vicinity, although with a degradedestimate of error associated with each of the received GNSS signals.This information may still prove useful to a GNSS receiver that has notyet resolved any biases of GNSS signals it has received. In the exampleof FIG. 4D, vehicle 206 passes by the roadside convergence data sharingsystem 110 prior to its having achieved convergence of its received GNSSsignals.

In accordance with other embodiments, the convergence data server of theroadside convergence data sharing system 110 and convergence data server101-6 of vehicle 206 automatically discover each other using the V2Vprotocols and establish communications. In the embodiment of FIG. 4C,the roadside convergence data server conveys to the convergence datasharing system of vehicle 206 that it needs convergence data. Inaccordance with various embodiments, the convergence data server 101-6of vehicle 206 will convey the convergence data to roadside convergencedata sharing system 110.

FIG. 4E shows the use of a system for sharing convergence data inaccordance with various embodiments. In FIG. 4E, a convergence datasharing system 110 comprises a convergence data server and a GNSSreceiver. A first vehicle 207 is equipped with a convergence datasharing system comprising convergence data server 101-7 and GNSSreceiver 111-7. A second vehicle 208 is similarly equipped with aconvergence data sharing system comprising convergence data server 101-8and GNSS receiver 111-8. Various embodiments may be implemented with awireless communication transceiver such as a cellular communicationtransceiver, or various implementations of a radio frequency transceiversuch as implementations of the IEEE 802.15 (ZigBee) standard that have alonger range than a typical IEEE 802.11p transceiver. In accordance withvarious embodiments, a plurality of wireless convergence data serverscan be implemented as a wireless mesh network communication system inwhich a first convergence data server can store and forward convergencedata to a second convergence data server. In the example of FIG. 4E, itis assumed that vehicle 208 has lost convergence either due toobstructions interrupting tracking of GNSS satellites or because it hasbeen shut down. Furthermore, while vehicle 207 is in communication withconvergence data sharing system 110 via communication link 256, vehicle208 is not in communication with convergence data sharing system 110.This may be due to having a short range communication device such asIEEE 802.11p transceiver or due to obstructions such as terrain thatimpede direct communication. In this example, convergence data server101-7 of vehicle 207 can store convergence data it has received fromconvergence data sharing system 110 and forward it to convergence dataserver 101-8 of vehicle 208.

FIG. 4F shows the use of a system for sharing convergence data inaccordance with various embodiments. In FIG. 4F, a convergence datasharing system 110 comprising a convergence data server and a GNSSreceiver is located along a highway. A passing vehicle 209 is alsoequipped with a convergence data sharing system comprising convergencedata server 101-9 and GNSS receiver 111-9. A second vehicle 210 issimilarly equipped with a convergence data sharing system comprisingconvergence data server 101-10 and GNSS receiver 111-10. Convergencedata server 101-9 is in communication with convergence data sharingsystem 110 and convergence data server 101-10 via communication links257 and 259 respectively. Similarly, convergence data sharing system 110is in communication with convergence data server 101-10 viacommunication link 258.

In this example, vehicle 210 may receive convergence data from bothconvergence data sharing system 110 and from convergence data server101-9 of vehicle 209 at the same time. In accordance with variousembodiments, for example, convergence data server 101-10 of vehicle 210can select which convergence data to use based upon various criteria. Inaccordance with one embodiment, convergence data server 101-10 ofvehicle 210 is configured to select convergence data based upon thebaseline distance. In other words, the distance between GNSS receiver111-10 and GNSS receiver 111-9 may be compared with the distance betweenGNSS receiver 111-10 and the GNSS receiver of convergence data sharingsystem 110 to determine which convergence data to use. As describedabove, in accordance with various embodiments, a given convergence dataserver may also convey its position fix with the convergence data. Inaccordance with various embodiments, convergence data server 101-10 ofvehicle 210 may determine which convergence data server is closer to itscurrent position and select that convergence data to use. In thisexample, vehicle 210 is closer to convergence data sharing system 110than vehicle 209. Therefore, in this example, convergence data server101-10 of vehicle 210 would use the convergence data received fromconvergence data sharing system 110.

It is noted that other criteria may be used by convergence data server101-10 of vehicle 210 instead of, or in conjunction with, the baselinedistance, to determine which convergence data to select in accordancewith various embodiments. For example, convergence error estimates maybe conveyed along with convergence data. The convergence error estimatesmay include how long continuous tracking of a given GNSS signal has beenmaintained. Typically, the longer a GNSS receiver has been continuouslytracking GNSS signals from a given satellite, the more refined thesolution of error estimates becomes. In other words, it is preferable toreceive convergence data from a receiver that has been continuouslytracking a given signal for a longer period. Thus, if vehicle 209 hasrecently passed under an overpass and lost tracking of a given signal,while convergence data sharing system 110 has maintained continuoustracking of that same signal, convergence data server 101-10 of vehicle210 may select the convergence data from convergence data sharing system110 based upon that criteria alone, or in conjunction with the baselinedistance between receivers as described above.

Another criteria that can be used in determining which set ofconvergence data to use is the constellation intersection size. Theconstellation intersection size is the intersection of the sets of GNSSsatellites concurrently tracked by two or more GNSS receivers. Forexample, GNSS receiver 111-10 of vehicle 210 may be tracking signalsfrom a set of GNSS satellites numbered 1, 2, 3, 4, and 5; GNSS receiver111-9 of vehicle 209 may be tracking signals from a set of GNSSsatellites numbered 2, 3, 4, 5, and 6; and the GNSS receiver ofconvergence data sharing system 110 may be tracking signals from a setof GNSS satellites numbered 1, 3, 5, 6, 7, and 8. In the presentexample, GNSS receivers 111-9 and 111-10 are concurrently trackingsignals from four satellites (e.g., satellites 2, 3, 4, and 5).Similarly, GNSS receiver 111-9 and the GNSS receiver of convergence datasharing system 110 are concurrently tracking signals from threesatellites (e.g., satellites 1, 3, and 5). Thus, constellationintersection size for GNSS receivers 111-9 and 111-10 is greater. Inthis example, convergence data server 101-10 of vehicle 210 may selectthe convergence data from convergence data server 101-9 based upon thelarger constellation intersection size.

Another criteria that can be used in determining which set ofconvergence data to use is receiver type. Similar receivers may havesimilar biases (e.g., estimates of antenna phase center and/or receivermeasurement biases). Thus a receiver may choose convergence data from asimilar receiver type.

Another criteria that can be used in determining which set ofconvergence data to use is age of convergence data. In some embodiments,newer convergence data (or convergence data that was obtained morerecently), may be selected over older convergence data.

It is noted that embodiments may use other/additional criteria inselecting convergence data from a given source and/or combinations ofcriteria. Additionally, various criteria may be weighted to assist indetermining which criteria is used in selecting convergence data. Forexample, a greater constellation intersection size may be given greaterweight than baseline distance between receivers. Thus, while GNSSreceiver 111-10 is closer to convergence data sharing system 110, theconvergence data from convergence data server 101-9 may be selected dueto the greater constellation intersection size.

With reference now to FIG. 5, a block diagram is shown of an exemplaryGNSS receiver 111 that may be used in accordance with variousembodiments described herein. In particular, FIG. 5 illustrates a blockdiagram of a GNSS receiver 111 in the form of a GPS receiver that iscapable of demodulation of L1 and/or L2/L2C/L5 signal bands receivedfrom one or more satellites. A more detailed discussion of the functionof a GNSS receiver can be found in U.S. Pat. No. 5,621,416, by Gary R.Lennen, titled “Optimized processing of signals for enhancedcross-correlation in a satellite positioning system receiver,” which isincorporated herein by reference.

FIG. 5 shows an example where GPS signals (L1=1575.42 MHz,L2/L2C=1227.60 MHz, and L5=1176.45 MHz) enter GNSS receiver 111 througha multi-frequency antenna 332 (that may be disposed within a housing ofGNSS receiver 111). Master oscillator 348 provides a referenceoscillator that drives all other clocks in the system. Frequencysynthesizer 338 takes the output of master oscillator 348 and generatesclock and local oscillator frequencies used throughout the system. Forexample, in one embodiment, frequency synthesizer 338 generates severaltiming signals such as a 1st (local oscillator) signal LO1 at 1400 MHz,a 2nd local oscillator signal LO2 at 175 MHz, an SCLK (sampling clock)signal at 25 MHz, and a MSEC (millisecond) signal used by the system asa measurement of local reference time.

A filter/LNA (Low Noise Amplifier) 334 performs filtering and low noiseamplification of the signals. The downconvertor 336 mixes the L1, L2,and/or L5 signal bands in frequency down to approximately 175 MHz andoutputs analog L1, L2, and/or L5 signal bands into an IF (intermediatefrequency) processor 350. IF processor 350 takes the analog L1, L2,and/or L5 signal bands at approximately 175 MHz and converts them intodigitally sampled in-phase (L1 I, L2/L2C I, and L5 I) and quadraturesignals (L1 Q, L2/L2C Q, and L5 Q). It is noted that the carrierfrequency bands discussed above are examples used in accordance withvarious embodiments and that other carrier frequency bands may be usedin accordance with the present technology.

At least one digital channel processor 352 inputs the digitally sampledL1, L2/L2C, and/or L5 in-phase and quadrature signal bands. Each digitalchannel processor 352 is designed to digitally track the L1, L2/L2C,and/or L5 signal bands from one satellite by tracking code and carriersignals. Each digital channel processor 352 is also designed to formcode and carrier phase measurements in conjunction with the GNSSmicroprocessor system 354. GNSS microprocessor system 354 is a computingdevice that facilitates tracking and measurements processes by providingpseudorange and carrier phase measurements for navigation processor 358.In one embodiment, GNSS microprocessor system 354 provides signals tocontrol the operation of one or more digital channel processors 352.According to one embodiment, the GNSS microprocessor system 354 providesone or more of pseudorange information 372, Doppler Shift information374, and Carrier Phase Information 376 to the navigation processor 358.One or more of pseudorange information 372, Doppler Shift information374, and Carrier Phase Information 376 can also be obtained from storage360. Alternatively, information can be obtained from outside of GNSSreceiver 111 such as from a convergence data server. One or more of thesignals 372, 374, and 376 can also be conveyed to a processor of anexternal device. In accordance with various embodiments, GNSSmicroprocessor system 354 is configured to output a position fix to adevice outside of GNSS receiver 111. Additionally, GNSS microprocessorsystem 354 can output a position, velocity, and time (PVT) solution to adevice outside of GNSS receiver 111. Navigation processor 358 performsthe higher level function of combining measurements in such a way as toproduce position, velocity and time information for differential andsurveying functions, for example, in the form of a position fix 380.Storage 360 is coupled with navigation processor 358 and GNSSmicroprocessor system 354. It is appreciated that storage 360 maycomprise a volatile or non-volatile storage such as a RAM or ROM, orsome other computer readable memory device or media.

In some embodiments, GNSS microprocessor system 354 and/or navigationprocessor 358 receive additional inputs such as correction data (e.g.,382). According to one embodiment, examples of the correction data areWAAS corrections, differential GPS corrections, RTK corrections, PPPcorrections, signals used by the Enge-Talbot method, EGNOS corrections,and wide area augmentation system (WAAS) corrections among others.

Although FIG. 5 depicts a GNSS receiver 111 with GPS navigation signalbands L1, L2/L2C, and L5, various embodiments are well suited fordifferent combinations of navigational signals used by other GNSSsystems. For example, according to one embodiment, the GNSS receiver 111may only have an L1I navigational signal band. According to otherembodiments, GNSS receiver 111 may use other combinations of navigationsignal bands.

With reference now to FIG. 6, all or portions of some embodimentsdescribed herein may be composed of computer-readable andcomputer-executable instructions that reside, for example, innon-transitory computer-usable/computer-readable storage media of aconvergence data server 101. That is, FIG. 6 illustrates one example ofa type of convergence data server 101 that may be used in accordancewith or to implement various embodiments of a convergence data serverthat are described herein. It is appreciated that convergence dataserver 101 of FIG. 6 is only an example and that embodiments describedherein can operate on or within a number of different systems including,but not limited to, embedded computer systems, server devices, variousintermediate devices/nodes, vehicular navigation systems, handheldcomputer systems, and the like. Convergence data server 101 of FIG. 6 iswell adapted to having peripheral computer-readable storage media 402such as, for example, a floppy disk, a compact disc, digital versatiledisc, universal serial bus “thumb” drive, removable memory card, and thelike.

Convergence data server 101 of FIG. 6 includes an address/data bus 405for communicating information, and a processor 430A coupled to bus 405for processing information and instructions. As depicted in FIG. 6,convergence data server 101 is also well suited to a multi-processorenvironment in which a plurality of processors 430A, 430B, and 430C arepresent. Conversely, convergence data server 101 is also well suited tohaving a single processor such as, for example, processor 430A.Processors 430A, 430B, and 430C may be any of various types ofmicroprocessors. Convergence data server 101 may also include datastorage features such as a computer usable volatile memory 411, e.g.,random access memory (RAM), coupled to bus 405 for storing informationand instructions. Convergence data server 101 may also include computerusable non-volatile memory 410 (e.g., read only memory (ROM)) coupled tobus 405 for storing information and instructions for processors 430A,430B, and 430C. Also present in convergence data server 101 is a datastorage device 102 (e.g., a magnetic disk, optical disk, or hard diskdrive) coupled to bus 405 for storing information and instructions.Convergence data server 101 may also include an optional alphanumericinput device 414 including alphanumeric and function keys coupled to bus405 for communicating information and command selections to processor430A or processors 430A, 430B, and 430C. In one embodiment, convergencedata server 101 may also include an optional display device 418 coupledto bus 405 for displaying information. It is noted that in accordancewith various embodiments, operations related to convergence sharing maybe implemented by processor(s) 430A, 430B, and 430C.

Convergence data server 101 may also include an I/O device 421 forcoupling convergence data server 101 with external entities such as, butnot limited to, GNSS receiver 111 and/or a cloud computing network.Although not depicted, in some embodiments convergence data server 101may include a GNSS receiver 111, which may be coupled with bus 405. Inaccordance with various embodiments, I/O device 421 may comprise one ormore interfaces with various networked devices. Examples of networkswith which I/O device 421 may be coupled include, but are not limitedto, Ethernet port(s), universal serial bus (USB) ports, and/or specialpurpose interfaces. For example, in one embodiment, I/O device 421 maycomprise a modem for enabling wired or wireless communications betweenconvergence data server 101 and an external network such as the Internetand/or cloud computing network 121.

Referring still to FIG. 6, various other components are depicted forconvergence data server 101. Specifically, when present, an operatingsystem 422, applications 424, modules 423, and/or data 428 are shown astypically residing in one or some combination of computer usablevolatile memory 411 (e.g., RAM), computer usable non-volatile memory 410(e.g., ROM), and data storage device 102. In some embodiments, all orportions of various embodiments described herein are stored, forexample, as an application 424 and/or module 423 in memory locationswithin RAM 411, computer-readable storage media within data storagedevice 102, peripheral computer-readable storage media 402, and/or othertangible computer readable storage media. In the embodiment of FIG. 6,convergence data server 101 may also include a wireless communicationtransceiver that is coupled with bus 405.

It is noted that convergence data server 101 may utilize multiplewireless communication transceivers operable in separate and distinctwireless communication networks, such as a first wireless communicationtransceiver compliant with the IEEE 802.11p specification forimplementing a DSRC communication network, and second wirelesscommunication transceiver comprising a cellular transceiver.

Unless otherwise specified, one or more of the various embodimentsdescribed herein can be implemented as hardware, such as circuitry,firmware, or computer readable instructions that are stored on anon-transitory computer readable storage medium. The computer readableinstructions of the various embodiments described herein can be executedby a hardware processor, such as central processing unit, to causeconvergence data server 101 to implement the functionality of thevarious embodiments. For example, one embodiment may comprise anon-transitory computer readable storage medium having computer readableinstructions stored thereon for causing a computer system (e.g.,convergence data server 101 or other computer system) to perform amethods described herein.

FIG. 7 is a flowchart of a method 800 for sharing convergence data inaccordance with various embodiments. In operation 801 of FIG. 7,convergence data is received at a mobile GNSS receiver via acommunication connection. In various embodiments, the convergence dataserver conveys convergence data to a converged or non-converged GNSSreceiver or to another server.

In operation 802 of FIG. 7, the convergence data is used to converge themobile GNSS receiver. As discussed above, a GNSS receiver operating in anon-converged state can use the received convergence data to achieveconvergence of its GNSS receiver almost instantly upon reception of theconvergence data.

It is noted that in accordance with various embodiments, authenticationprocedures may be implemented between convergence data servers toprevent spoofing. This prevents the introduction of false convergencedata into the system. Furthermore, the convergence data may be encryptedor subjected to an encryption hash function to prevent spoofing orun-authorized access to the convergence data sharing systems.

CONCLUSION

Example embodiments of the subject matter are thus described. Althoughthe subject matter has been described in a language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexamples of implementing the claims.

Unless specifically stated otherwise, as apparent from the foregoingdiscussions, it is appreciated that throughout the description,discussions utilizing terms such as “receiving,” “utilizing,”“determining,” “deriving,” “calculating,” and “generating” refer to theactions and processes used to transform the state of a computer system,data storage system, storage system controller, microcontroller,hardware processor, or similar electronic computing device orcombination of such electronic computing devices. The computer system orsimilar electronic computing device manipulates and transforms datarepresented as physical (electronic) quantities within registers andmemories into other data similarly represented as physical quantitieswithin the memories or registers or other such information storage,transmission, or display devices.

Various embodiments have been described in various combinations andillustrations. However, any two or more embodiments or features may becombined. Further, any embodiment or feature may be used separately fromany other embodiment or feature. Phrases, such as “an embodiment” or“one embodiment,” among others, are not necessarily referring to thesame embodiment. Features, structures, or characteristics of anyembodiment may be combined in any suitable manner with one or more otherfeatures, structures, or characteristics.

What is claimed is:
 1. A method for sharing convergence data betweenGlobal Navigation Satellite System (GNSS) receivers, the methodcomprising: receiving convergence data at a first mobile GNSS receiverfrom a second mobile GNSS receiver, the first mobile GNSS receiveroperating in a non-converged state and the second mobile GNSS receiveroperating in a converged state, the convergence data generated at thesecond mobile GNSS receiver using correction data from one or more basestations, the convergence data comprising at least one of correctionbias errors estimated by the second mobile GNSS receiver or correctiondata refined using the correction bias errors estimated by the secondmobile GNSS receiver, wherein the correction bias errors compriseadjustments to at least one of orbit models or satellite clocks providedwith the correction data from the one or more base stations; andthereafter determining a position of the first mobile GNSS receiverusing the convergence data from the second mobile GNSS receiver.
 2. Themethod of claim 1 wherein at least one of the first mobile GNSS receiveror the second mobile GNSS receiver is associated with a vehicle.
 3. Themethod of claim 1 wherein the convergence data is Precise PointPositioning (PPP) convergence data.
 4. The method of claim 1 wherein thefirst mobile GNSS receiver is configured to receive GNSS signals in onefrequency band, and the second mobile GNSS receiver is configured toreceive GNSS signals in at least two separate frequency bands.
 5. Themethod of claim 1 wherein the convergence data is received at the firstmobile GNSS receiver using a wireless communication transceiver.
 6. Themethod of claim 1 wherein the convergence data includes atmosphericmodels.
 7. The method of claim 1 wherein the convergence data includesresolved carrier phase ambiguities.
 8. The method of claim 1 wherein theconvergence data indicates how long continuous tracking of GNSS signalsfrom particular satellites has been maintained.
 9. The method of claim 1wherein the convergence data is generated at the second mobile GNSSreceiver using PPP correction data from a network of base stations. 10.A system for sharing convergence data, comprising: a convergence dataserver comprising: a data storage device configured to store PrecisePoint Positioning (PPP) convergence data for a first mobile GlobalNavigation Satellite System (GNSS) receiver, the PPP convergence datagenerated by the first mobile GNSS receiver using correction data fromone or more base stations, the PPP convergence data comprising at leastone of correction bias errors estimated by the first mobile GNSSreceiver or correction data refined using the correction bias errorsestimated by the first mobile GNSS receiver, wherein the correction biaserrors comprise adjustments to at least one of orbit models or satelliteclocks provided with the correction data from the one or more basestations; and a communication transceiver coupled with said data storagedevice and configured to convey said PPP convergence data to a secondcommunication transceiver; and a second mobile GNSS receiver operatingin a non-converged state and coupled with the second communicationtransceiver and configured to use the PPP convergence data to convergesaid second mobile GNSS receiver.
 11. The system of claim 10 wherein thefirst mobile GNSS receiver is disposed in a first vehicle and the secondmobile GNSS receiver is disposed in a second vehicle.
 12. The system ofclaim 10 wherein the second mobile GNSS receiver is arranged in avehicle and the first mobile GNSS receiver is disposed in aninfrastructure other than a vehicle.
 13. The system of claim 10 whereinthe second mobile GNSS receiver is configured to receive GNSS signals inat least two separate frequency bands.
 14. The system of claim 10wherein the communication transceiver and the second communicationtransceiver communicate via a wireless communication connection.
 15. Thesystem of claim 10 wherein the communication transceiver and the secondcommunication transceiver are compliant with the Dedicated Short-RangeCommunications (DSRC) standard.
 16. The system of claim 10 wherein theconvergence data server comprises a cloud computing network.
 17. Amethod for sharing convergence data between Global Navigation SatelliteSystem (GNSS) receivers, said method comprising: receiving Precise PointPositioning (PPP) convergence data at a first mobile GNSS receiver via acommunication connection, the first mobile GNSS receiver operating in anon-converged state and the PPP convergence data provided by a secondGNSS receiver operating in a converged state, the PPP convergence datagenerated by the second GNSS receiver using correction data from one ormore base stations, the PPP convergence data comprising at least one ofcorrection bias errors estimated by the second GNSS receiver orcorrection data refined using the correction bias errors estimated bythe second GNSS receiver wherein the correction bias errors compriseadjustments to at least one of orbit models or satellite clocks providedwith the correction data from the one or more base stations; andutilizing the PPP convergence data to determine a position of the firstmobile GNSS receiver.